Embodiments of the present invention relate to erasing a storage medium and, in particular embodiments, to erasing a disk surface.
There are several methods utilized in the related art to achieve erasure of media. A bulk erase is a common, but inconvenient process. In a bulk erase, the media is removed from a drive and erased. The drive is then reassembled. This necessitates making mechanical changes to the drive.
Another method in the related art is a servo-track-writer erase. The servo-track-writer writes servo information, which includes identification information and burst patterns on a magnetic disk. The servo-track-writer writes this information onto the magnetic disk in part by pressing a pushpin against an actuator on which a magnetic head is mounted. This necessarily involves uncovering the hard disk drive and, thus, requires that the servo information write must be performed in a clean room. The servo-track-writer erase also involves utilizing the pushpin to control the write head of the drive, which again consequently requires the use of a clean room, along with the aforementioned inconvenience of making mechanical changes to the drive. Further, the use of a servo-track-writer involves an addition of machinery to the drive that is costly.
A third method in the related art is a random windshield wiper erase, which involves random motions of a voice coil motor with DC erase current. Because the motions are random, there is no guarantee that all of the media is erased; rather an amount of the media that is erased depends upon an ability to correct for errors; The major disadvantage of this method is head degradation associated with the write current at the head during a seek across a textured landing zone boundary. For ramp load/unload designs, the use of write current through the head when the head hits the ramp impacts an effectiveness and lifetime of the head. It is important to turn off the write current through the head as the head is hitting and moving up to the ramp. This is because there is a potential for head failure and thermal damage to the head if the head is writing without an air bearing between the head and the disk surface. Thus, there may be problems with using random motions for erase with ramp load/unload products.
A fourth method in the related art is an in-drive bulk DC erase. This method also necessitates mechanical changes to the drive.
Further, with regard to ex-situ multidisk writers, it could be advantageous to efficiently erase a disk without having to remove it from an ex-situ multidisk writer, particularly with writers that are able to do verification on the servo patterns that are written. For example, if a spindle of 10 to 15 disks were written, and a large number of those failed servo verification, it might be advantageous to erase each of the failed disks and be able to write them again without having to unload them to a bulk eraser.